MICROWAVE IMAGE UNDERSTANDING AND ITS APPLICATION TO RADAR CROSS-SECTION MANAGEMENT.

摘要

In this dissertation the basic scattering properties of a perfectly conducting object are briefly reviewed. In the high frequency region, the scattered field of a complex shaped object can be attributed to a combination of several mechanisms. The advent of high resolution radar enables us to consider each scattering mechanism separately. The microwave image of a conducting object is interpreted from a new approach, based on the understanding of the scattering mechanism and the image reconstruction algorithm. The connection between various scattering mechanisms and their reconstructed images is then established. From this we can interpret what the image represents and predict what the image will look like for given spectral and angular windows. Several numerical and experimental examples have been included to support this new interpretation approach.; A new algorithm to extrapolate the available data into the missing bands is devised.; A new term, "diaphanization", defined as the techniques of reducing RCS and the techniques of obscuring an image is introduced. RCS management is considered not only from a detection perspective, namely the reduction of the target's RCS to elude radar detection, but also from the image point of view where disguising of a targets's appearance to impede recognition by an imaging radar is sought. The procedure which employs microwave diversity imaging to diaphanize a target over prescribed spectral and angular windows is given and the robustness of the diversity imaging system to the Gaussian noise is demonstrated. Some rules for distorting an image are proposed. These rules are: create artificial discontinuities, create multiple reflections and make the reflectivity at any given point a function of time.; Traditional techniques for reducing the RCS are applied to RCS management studies. These techniques are by covering absorber material, target shaping, and impedance loading. The theory pertaining to absorber-covered bodies is reviewed and the theoretical background for obscuring an image by absorber covering based on the physical optics approximation is established. (Abstract shortened with permission of author.)